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A female hawkmoth reared from a caterpillar found on Wimbledon Common. By Dr Ian Kitching

Moths and bats: An evolutionary war

By Katie Pavid

First published 16 February 2016

It is a battle that has been raging in the skies for 60 million years. Bats and moths have been up against each other under cover of darkness, fighting for survival in an evolutionary arms race.

By studying how the two creatures interact, scientists are learning about the secret lives of moths and how they outwit their biggest predators.

Dr Ian Kitching, a researcher at the Museum, has spent decades studying different species of hawkmoth, a group of insects found everywhere from the tropics to the UK.

Some of his latest work is a collaboration with Dr Akito Kawahara of the Florida Museum of Natural History and Dr Jesse Barber of Boise State University.

It involves looking at exactly how and why these moths found themselves in an evolutionary conflict with bats, and how they are coming out on top.

Ancestral manoeuvres in the dark

It was nearly 100 years ago that scientists first noticed male hawkmoths rubbing their genitals against their abdomens, giving off a high-pitched, ultrasonic squeak.

It is thought the squeaking is emitted to attract the attention of females, but it has the added benefit of confusing predators.

The rear of a male hawkmoth, showing the stridulatory scales that generate ultrasound.

Bats rely on ultrasonic echolocation, or sonar, to find prey, allowing them to catch victims with ease in the dark. But scientists have found that when it comes to hawkmoths, bats can get confused during the hunt and are unable to capture them.

It is one aspect of an evolutionary competition that has been going on for millions of years, with bats and moths developing new adaptations to outmanoeuvre each other.

Kitching said: 'This ultrasonic sound the moths give off is jamming the sonar of the bats, confusing them and meaning they miss their target at the last second.

'We still don't know exactly why it first evolved, but in all the species that make the noise, the males have to go to a lot of effort to impress a female. This may have been the original use for the sounds. It was then co-opted as a means of defence, temporarily confusing the bats when they swoop in for the kill.'

Many species of bat rely on echolocation to capture their prey.

Bats fighting back

It is estimated that hawkmoths starting producing ultrasound around 26 million years ago, and the race has been going on ever since.

But the moths are not having it all their own way.

Some bats are getting round the problem by using echolocation at a frequency or pitch the moths cannot detect. Instead of catching moths in flight, bats can also pick them off leaves and branches while the moths are resting.

Such changes in the ways moths and bats try to get the better of each other is an example of co-evolution, and it is still going on today as they battle for survival in the night skies around the world.